This invention relates generally to fluidic processing of biological samples for diagnostic purposes, sedimentation or centrifugal pelleting of suspended particulate matter, such as cells, separating particulate matter based on density, and enumerating particulates or cells by measurement of packed volume. More specifically, this invention relates to male fertility testing, and, in particular, sperm cell counting.
Worldwide, 10-20% of couples that attempt to conceive a new child have sub-optimal fertility. Difficulty in conceiving may be due to defects in either the male or the female reproduction system or a combination of the two, or due to other contributing factors. In approximately 40% of cases of infertility, the male partner is a contributing factor. The primary metrics available to evaluate male fertility are sperm count and motility. Sperm count is a concentration of sperm cells in semen and motility is a percentage of sperm cells capable of movement.
Conventional methods of evaluating male fertility comprise conducting clinical tests including microscopic examination to measure sperm count and motility. Semen samples for the clinical tests must be provided at the site of examination leading to privacy concerns for male subjects. Furthermore, providing a semen sample at the site of examination or in a clinical setting is widely perceived as awkward or embarrassing. This perception can deter male fertility testing for couples with difficulty conceiving despite the high prevalence of male fertility issues. A semen analysis test suitable for use in the home may be useful in cases where aversion to clinical conditions would otherwise deter testing. A few semen analysis test kits have been developed for use in the home, such as those in which a colored line is displayed when the concentration of sperm cells in a sample exceeds a particular number (e.g., 20 million per mL) or a color change is displayed when concentration of viable sperm cells in a sample exceeds a particular number (e.g., 10 million per mL). In these examples of test kits, the semen analysis tests provide a non-quantitative evaluation of sperm count. In cases where a low sperm count is correctable or sperm count varies over time, it may be desirable to have a quantitative estimate of the absolute sperm count and motility.